


Riptide Lover Remix: Firsthand Research

by jinglebell



Category: Sherlock (TV)
Genre: Anal Sex, Domination, Forced Orgasm, Interspecies Sex, Johnlock - Freeform, M/M, Merlock, PWP, Porn Without Plot, Prostate Massage, Prostate Milking, Riptide Lover, Riptide Lover spinoff, Rough Sex, Size Difference, aulock, crying during conensual rough sex, huge cock, mermaid, merman, orca cock, size queen, sublte masochism, unusual anatomy
Language: English
Status: Completed
Published: 2019-10-07
Updated: 2019-10-07
Packaged: 2020-11-24 14:08:00
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,779
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20908910
Author URL: https://archiveofourown.org/users/jinglebell/pseuds/jinglebell
Summary: A Riptide Lover spinoff in which John is the undine. Sherlock is arse-fucked by a merman on an abandoned dock. He loves it.A companion piece toRiptide Lover.





	Riptide Lover Remix: Firsthand Research

**Author's Note:**

  * Inspired by [Riptide Lover](https://archiveofourown.org/works/2312978) by [jinglebell](https://archiveofourown.org/users/jinglebell/pseuds/jinglebell). 

> This one is dedicated to [Redscudery](http://archiveofourown.org/users/redscudery/pseuds/redscudery) because I miss her and she will see all of my unedited purple prose and be amused.
> 
> Written in one sitting, unbeta’d, just a total impulse fic that I will post before I overthink it! Thanks for your patience with mispellings, grammatical hiccups, and/or repetitious use of the words "ache" or "swollen".

“John-!” Sherlock sobbed, flat on his back with his knees hiked over his shoulders. John's cock split him open like hot steel. The smooth wood of the old dock was sun-warm, but John's scales were cool where they pounded his arse with each thrust. Sherlock was impossibly full, stretched wide open with a burn that satisfied some primal need. The oil bottle was knocked over in the festivities. It bobbed in the waves.

There was something filthy about being fucked in broad daylight. Sherlock imagined what people would think if they could see him now, legs spread for a mythological fiction. What would his brother think? What would Lestrade say if he knew! However, the only voyeurs were the beach gulls, and they were busy combing for dead things. Sea water sloshed up in a carnal typhoon about John's tail. 

_ I underestimated his weight. Closer to seventeen -- no, eighteen -- stone. The tail is pure muscle. Oh-! _

The tail wasn’t the only thick muscle. John held himself up on one hand, with the other crushing Sherlock’s ankles together by his ears. It would bruise. Probably already had. He wished John would crush harder. He was bloody strong, and not afraid to throw his weight around in the interest of a good fuck. Sherlock appreciated that. A great deal. His previous sexual partners had treated him like spun glass. Tedious. They had been tedious, and then there was _John_, and John was Not Tedious At All, In Fact.

_John--!_

Sherlock had encountered John entirely by accident. John wasn't really his name, but human vocal cords struggled with the diaphanous chorus of vowels and clicks that was his name. Sherlock had tried to use it. Several times. Until John had quietly put his webbed fingers all the way into his mouth, and his cock all the way into his arse, to make him shut up.

Months ago, Sherlock had climbed too far across the sea rocks. Focused on his purpose, the tide had snuck up on him. He had no choice but to flee farther out from civilization, his bare feet sliced and bruised. He came upon a secret cove. It was shaded by shelves of rock and draping sheets of foliage from above. The sand was a carpet darkened by the receding tide. That was when he saw two merfolk. At first, Sherlock thought they were embracing -- but no, that was incorrect.

They were fighting.

Mesmerized, Sherlock ducked behind a crest of sea stone. He watched them in what was unmistakably combat. A channel of churned sand drew a line from the sea. They had somehow wrested themselves out of the water. Their bodies were huge and lithe. Their human halves twisted and their fan-tails thrashed clumsily in the sand. Scales caught the light intermittently. Both vibrated with fury, neck-gills flared out like lace collars. 

The one on top was larger. It had lobster-red scales that flashed as it bore down on the other. The one beneath it was more finely formed. It had bright copper scales, closer to yellow than brown. Of the two, the red one seemed less invested. It seemed to be focused primarily on knocking away the smaller one. Then the smaller one found an opening and ripped open a the other's rib-gill. _A rib-gill!_ The owner of said rib-gill let out a feminine shriek. 

_ Female? Interesting! _

She reared up and made a deep and guttural bark. Sherlock felt his ears vibrate, a sudden buzzing of ossicle that made him nauseous. The sand around the sirens exploded into the air like gunpowder. The little copper one was greatly affected by this; it went stiff and palsied, eyes rolling white. The big female took this opportunity to yank away, shoving herself backward on across the sand. She paused half-in the surf. Sherlock was afraid, for a moment, that she had seen him. However, her attention remained with the other. He thought the expression on her humanlike face was rather longing.

The copper one recovered, laying flat on its back and gasping. From her safe distance, the female made a hopeful click. She received a gurgling snarl in response, and so she swam away.

_I wonder what merfolk have to quarrel about_, thought Sherlock. His blood thrummed. The existence of merfolk did not throw him so much as the intensity of what he had just born witness to. He watched the copper siren slump in the sand, settling in for what he assumed would be a slow recovery. Sherlock had forgotten to blink, so he closed his eyes to wet them. When he opened them, the merman was within touching distance, lifting its upper body on Sherlock's hiding-rock.

If Sherlock had the breath to scream, he would have. The siren had crept up upon him with the silence of a stalking leopard. Utterly silent. Quick as a viper. It could have torn out his throat, but it was waiting for him. Slowly he turned his head and their eyes met. _A male._ His eyes were dark blue. His pupils were inhuman, bringing to mind an octopus or some alien creature. He was much larger than he had seemed when pinned beneath the huge female. They regarded each other. It was a moment frozen in time. A moment that by all accounts should have been Sherlock's last.

Instead, Sherlock felt a frisson of electricity ripple through his heart. The frisson went down his belly, a burst of emotion he could not describe, and he exhaled a shuddering breath and said, "How interesting."

At any rate, that was how John and Sherlock met, and eventually they became familiar with each other, and now they were fucking. Right now, in fact. Sherlock grunted as the sore furl of his arsehole was opened again and again by that enormous cetacean cock, a rhythm made punishing for John’s stamina. He could not prevent the gasps that spilled from his lips. His cock was stiffly purple on his seed-slick belly. They had both climaxed already. Sherlock felt like an abused piece of meat. It was glorious. Tears burnt down his cheeks; it was too much, overstimulating, his balls ached. John ducked down and licked his tears.

“P-Please--”

The merciless pendulum of John’s cock beat at the swollen gland inside of him, massaging it raw and painful. Sherlock's cock dribbled. His balls drew up high and tight, the tendons in his thighs screaming. He tried to cry out, tried to beg for mercy, John could fuck the wet hug of his throat, have the spidery length of his fingers, anything but his poor abused arse -- but John knew the true signal to stop and continued his business. John chuckled breathlessly at Sherlocks faux-pleas.

Sherlock felt it building and it hurt, the pain and pleasure now equal, and his third paroxysm was hammered out of him in a weak white spurt. Their bodies made small wet noises. It felt like his soul was being milked out of Sherlock's body. His legs were locked up and numb, and the node deep inside was so swollen and achey he felt it every time he breathed. John groaned in amazement. He pulled out, cock fat and jerking as it slung long white ropes all the way up Sherlock's lean body, painting his belly and chest and neck and face, and getting stuck in his curls. Sherlock watched him blurrily. He opened up stiff arms and John fell into them. Sharp teeth grazed the still-healing bite on Sherlock's neck. He turned his head a little to provide access. John shuddered. His chest vibrated in a comforting low purr.

“I like when you Sing,” Sherlock commented.

John flushed a little. “I was never any good at Singing.” When he spoke, the low drone continued uninterrupted. It seemed to come from a different source than his vocal cords. 

“Pish.”

“You have not heard the others. You have no basis for comparison.”

“Still, I like it.”

John ducked his head into the crook of Sherlock’s neck and hid.

They lay there for a half-hour. Eventually, Sherlock rolled away onto his side and cleaned himself. He watched John. John's chin was pillowed on his forearms on the dock. For an undine, John was brawny. Small and tan with blond hair shorn short with razor shells. He had communicative lines at the corners of his mouth. He smiled up at Sherlock.

Sherlock said, "Your ear-fins have changed color, recently. They're going a bit pink. Why?"

John's shoulders tensed. 

"And your tail-fins as well, I notice. Are you well?"

"Perfectly," grit John.

“John?” Sherlock sat up carefully. Seed drizzled from his sore arse and he was sitting in a spreading puddle of it. He did not have to fake his wince. John seized upon this opportunity to change the subject.

“I’ve hurt you.”

“Why are your fins changing color?”

John’s brow wrinkled. “I don’t want to hurt you.”

“I liked it. Now answer my question.”

John lifted himself and began to pull himself toward the edge. “Right. I’ll be going.”

Sherlock lurched forward to snatch John’s wet forearm. “Wait.”

John tried to pull free, but Sherlock clung harder. If the undine really wanted to leave, he would have shaken Sherlock off like a gnat. “I shall die if I do not know. I shall die immediately.”

Despite himself, John snickered. “You will not.”

“I shall. I shall waste away here on this dock and become a tedious, dead skeleton. It will be your fault.”

Cuttlefish-pupil eyes regarded him with amusement. “Well. Let me get into the water at least, I am thirsty.”

Sherlock released him and watched John’s head pop back out wet. “I don’t know how to say it in English. The color changes when it is time for me to breed. It's inconvenient.”

_Oh._ “Oh.”

“Oh,” echoed John.

"Fascinating," breathed Sherlock. "How long until..?"

"Mm. Several 'days'."

"Where will I meet you?"

John blinked and then burst into laughter. "Meet me?"

“Yes. I will be with you, of course, so. Where will we meet?" 

"Erm. It's a little more complicated than..."

Post-orgasm, Sherlock made a giddy little chirp. It was an undine sound. He once heard John make it in a specific context. John's chin jerked up; Sherlock caught it gently in his hand. They regarded each other. John’s cold hand gripped Sherlock’s wrist, turning it so he could plant a kiss. “I admit, I would have you with me. Still, we need to work out a plan. We will discuss it tomorrow, you impossible beauty."

Sherlock preened a little. He liked when John complimented him. They kissed and they parted for the night, and a week later Sherlock became intimately familiar with the Riptide.

**Author's Note:**

> Someone please draw undine!John.


End file.
